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What is the carbon payback period for a wind turbine?

4 September 2019

What is the carbon payback period for a large wind farm, taking into account the energy and resources used for materials, manufacture and the construction of supporting infrastructure? If it is long, say 30 years, are they worth it?

Angela Cotton, Southampton, UK

In 2006, turbine manufacturer Vestas studied the carbon payback period for various turbines. This took into account extraction and manufacturing of raw materials, production of the turbines, their transport, erection, operation, maintenance, dismantling and disposal, and the same for their foundation and the transmission grid. The figure was between seven and nine months, depending on the type of turbine. Other analyses have come up with similar figures.

Even taking into account the carbon emitted in transportation and installation of turbines, the payback period is nothing like the 30 years the questioner suggests. It is also worth noting that wind turbines can be recycled at the end of their lives.

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Linda Latham, Biggar, South Lanarkshire, UK

The question is both easy and difficult to answer. Easy because it can never just be about the cost in financial terms. Difficult because the exact time is subject to many influencing factors including wind, weather and pollution rates from industry.

Wind farms reduce the amount of power needed to be produced from other carbon producing sources. And they are less costly to build and maintain than other low-carbon systems, such as hydroelectric and nuclear power plants.

They may look an eyesore and seem to be on the march, but remember when power lines sprang up across our countryside allowing us all to access electricity? Now we hardly notice they are there.

Daniel Baird, Cirencester, Gloucestershire, UK

Several wind turbine life-cycle assessments have been undertaken and are available online. An onshore wind turbine can be expected to repay this energy debt in between about six and nine months of operation.

Offshore wind turbines take a little longer, their marginally higher generation outweighed by the extra steel needed. Beyond 30 years, even with refurbishment if necessary, the energy return on investment just gets better.

Alex Hromas, Sydney, Australia

This question is often based on the premise that renewable energy systems are built by people who are technically and financially naive. This is not the case.

In the UK, for example, sites are chosen on the basis of wind data from the Met Office. Actual wind conditions are then measured for several years to assess the viability of the site. The resulting assessment becomes a bankable document that is used to secure finance for the project from bankers. There are then negotiations with grid operators and power consumers, among whom there is no mention of saving the planet or tree hugging.

The embodied energy of the project and associated carbon is represented in the capital expenditure of the build. If this cost cannot be covered, the project is a no-go.

It is also worth bearing in mind that once such an installation is paying its capital cost and covering its maintenance, any energy generated in excess of that has a very low marginal cost – an extremely important economic consideration.